1. Field of the Invention
The present invention relates to a solid catalyst for preparing ethylidene diacetate and to methods for preparing and using that catalyst in a continuous process for manufacturing ethylidene diacetate represented by the following formula: ##STR1##
2. Background of the Invention
Various methods for producing ethylidene diacetate are known in the art. In all of these methods ethylidene diacetate has been prepared in batch reactor systems. Because known processes for preparing ethylidene diacetate employ a homogeneous catalytic reaction, there have been no known attempts to prepare this product by a continuous process. Conventional methods for preparing ethylidene diacetate have used homogeneous catalysts, e.g., transition metals such as rhodium, ruthenium, palladium and platinum. Difficulties arose in separating these homogeneous catalysts from the reaction product.
The most used preparation method employs oxygen to oxidize vaporized acetic acid and ethylene. In another method methyl acetate, carbon monoxide and hydrogen are reacted in a homogeneous catalyst system to yield ethylidene diacetate. This latter method suffers from several significant disadvantages, including the complexity of the reaction process and difficulties associated with separating and purifying the reaction product from the catalyst.
Other prior methods for producing ethylidene diacetate are disclosed in European Patent No. 0028474 and Japanese Patent No. 51-115409. The methods disclosed in these patents also suffer from similar difficulties associated with separating and purifying the product from the catalyst after completion of the reaction. These difficulties also are the result of the ethylidene diacetate being prepared using batch reactor systems.
A continuous method for producing acetic anhydride was disclosed in U.S. Pat. No. 4,046,807. In this method acetic anhydride was synthesized by a continuous process using a supported catalyst containing 13.2 weight percent rhodium and having the formula RhCl.sub.3.x H.sub.2 O.KI/activated charcoal. The yield of acetic anhydride using this continuous processing method was 6.76%.
The present invention is the first known continuous processing method capable of synthesizing ethylidene diacetate. The present method employs continuous reaction conditions and has produced yields, based on methyl acetate, of at least 20.4 % under similar conditions to those employed in the '807 patent.
The present invention, by providing a continuous process using a heterogeneous catalyst, both solves the problem of catalyst separation which plagues conventional batchwise processes and produces a better yield than obtained in prior continuous processes for producing acetic anhydride.